“Laser microdissection” refers to a method with which, in the field of medicine and microbiology, a small piece (called the “dissected specimen”) is cut out of a usually planar sample, for example cells or a tissue section, using a finely focused laser beam. The cut-out piece is then available for further biological or medical, for example histological, examinations. A laser microdissection unit of the kind just recited comprises a microscope having an illumination beam path directed onto the sample, and an imaging beam path that images the sample. A laser supplies a laser beam that is coupled into the microscope and directed onto the sample. With the focused laser beam, a piece is cut out of the sample. The laser microdissection unit furthermore encompasses a fluorescence device that comprises, in known fashion, a dichroic beam splitter and a blocking filter.
One such unit is, for example, the Leica AS LMD of Leica Microsystems Wetzlar GmbH. It comprises an upright microscope into whose optical incident-light axis the laser beam is coupled and is directed from above through the objective onto the sample to be cut. The incident-light axis, with the laser beam passing through it, can comprise lenses, diaphragms, or beam scanners for the laser beam, and is therefore also referred to as a “microdissection beam path.” An additional fluorescence axis is arranged above the incident-light axis. This fluorescence axis encompasses the complete fluorescence illumination system with a light source and optical system, as well as the conventional fluorescence cube with an excitation filter, dichroic beam splitter, and blocking filter. The arrangement of the fluorescence axis above the microdissection beam path allows simultaneous fluorescence observation and microdissection. The fluorescence axis is manually operated (e.g. switched over). Because the fluorescence axis is placed onto the microscope above the microdissection beam path, no installation space or access exists for motorizing the switchable components in the fluorescence axis.
Other research microscopes possess a higher degree of automation, also providing motorized and/or automated switchovers of components of the fluorescence axis. These research microscopes having a higher degree of motorization or automation therefore usually contain a fluorescence axis integrated into the stand. A laser cannot then, however, be coupled in.